Support is requested for years 35-40 of a long-standing training program in cancer research for postdoctoral fellows at the Fox Chase Cancer Center. The Training Faculty consists of 47 Mentors (11 Assistant Professor, 15 Associate Professor, 21 Full Professor) with diverse interests in cell growth control, signal transduction, oncogenes and tumor suppressor genes, angiogenesis, epigenetics, cancer prevention, programmed cell death, bio-behavioral cancer research, immunology, mouse models of cancer, and developmental therapeutics. The well-funded and highly collaborative Training Faculty come from five different research programs: Immune Cell Development and Host Defense, Cancer Biology, Developmental Therapeutics, Women's Cancer, and Cancer Prevention and Control. The postdoctoral pool is extremely strong; there are 4 applicants per open slot, and the majority of applicants received graduate training at outstanding Institutions and are published in high- impact journals. The program offers diverse training in areas relevant to cancer research, with a combination of didactic and laboratory-based training, including seminar series, journal clubs, grant- writing workshops, and educational series. Input from the postdoctoral pool is extensive and highly valued; trainee satisfaction is best exemplified by our placement, every year for the past seven years, in the Top 20 Best Places in the United States for Postdoctoral Training, as determined by anonymous survey and published in The Scientist magazine. Funding for 10 trainees per year is requested; this is less than one quarter the citizenship-eligible trainees in the labs of the training faculty. Trainee slots are highly competitive and have been continuously filled for the last 2 funding cycles. Finally, 82% of trainees who have completed training and left this program report that they are still doing research directly relevant to cancer, indicating that we are fulfilling our goal of training the future of cancer research. Finally, this training program serves as the nucleus of our postdoctoral program. Its continued success is vital to the mission of Fox Chase Cancer Center.